Abstract:

This invention relates to a safety needle pack to prevent needle stick
injuries. The safety needle pack comprises a hollow needle, a needle hub
surrounding the hollow needle, a slidable sleeve slidably mounted on the
needle hub and a pack surrounding the needle, hub and sleeve. The
slidable sleeve is adapted to slide between an extended position in which
the injection end of the needle is located inside the slidable sleeve and
a retracted position in which the injection end of the needle projects
from the slidable sleeve, via an intermediate position between the
extended position and the retracted position in which the injection end
of the needle projects partially from the slidable sleeve. The pack is
releasably mounted on the needle hub and slidable sleeve such that the
injection end of the pack covers the tip of needle. By causing the pack
to be moved towards the syringe, the pack retracts the slidable sleeve
from the extended position to the intermediate position.

Claims:

1. A safety needle pack comprising a hollow needle having a tip for
injecting into a patient, a needle hub surrounding the hollow needle, a
slidable sleeve slidably mounted on the needle hub and a pack surrounding
the hollow needle, needle hub and slidable sleeve,the needle hub, the
slidable sleeve and the pack having a receiving end which is distal to
the tip of the needle and an injection end which is proximal to the tip
of the needle,wherein the receiving end of the needle hub is suitable for
connection to an injection device and the slidable sleeve is adapted to
slide in the direction of the length of the needle between an extended
position in which the needle tip is located inside the slidable sleeve
and a retracted position in which the needle tip projects from the
slidable sleeve, via an intermediate position between the extended
position and the retracted position in which the needle tip projects
partially from the slidable sleeve, such that, in use, the slidable
sleeve is moved in to the intermediate position for injection in to the
patient and then as the needle is inserted into the patient, the slidable
sleeve is caused to move into the retracted position, and in moving in to
the retracted position a resultant force is generated such that on
removal of the needle from the patient the resultant force causes the
slidable sleeve to move towards the injection end of the needle hub and
into the extended position, the safety needle further comprising a
locking mechanism capable of retaining the slidable sleeve in the
extended position after removal of the needle from the patient,and
wherein the pack is releasably mounted on the needle hub and slidable
sleeve such that the injection end of the pack covers at least the needle
tip and the receiving end of the pack has an open portion to expose the
receiving end of the needle hub, and by causing the pack to be moved in a
direction towards the receiving end of the needle hub, the pack engages
with the slidable sleeve which is retracted from the extended position to
the intermediate position.

2. A safety needle pack as claimed in claim 1, wherein the open portion is
covered by a releasable membrane.

4. A safety needle pack as claimed in claim 1, wherein the injection end
of the pack has an extended portion which is capable of housing the
needle tip in the intermediate position.

5. A safety needle pack as claimed in claim 1, wherein the needle hub has
one or more projections which abut against one or more shoulders on the
inside of the pack when the slidable sleeve is in the intermediate
position.

6. (canceled)

7. A safety needle pack as claimed in claim 1, wherein the pack is made
from a plastic material.

8. A safety needle pack as claimed in claim 1, wherein the needle hub has
an outer surface which is adapted to deflect the slidable sleeve as, in
use, the needle is inserted into the patient, and the slidable sleeve has
a radially elastically deformable portion such that, in use, the
resultant force is generated within the slidable sleeve as the slidable
sleeve is caused to move towards the receiving end of the needle hub and
into the retracted position.

9. A safety needle pack as claimed in claim 1, wherein at least part of
the receiving end of the needle hub has a tapered outer surface which
tapers towards the injection end and the slidable sleeve has a radially
elastically expandable portion.

10. A safety needle pack as claimed in claim 9, wherein the outer surface
of the receiving end of the needle hub has a substantially conical shape
which tapers towards the injection end.

11. A safety needle pack as claimed in claim 8, wherein the slidable
sleeve has at least one cantilever arm which bears resiliently on the
tapered outer surface of the needle hub and, in use, as the needle is
inserted into a patient, the at least one cantilever arm is displaced
outwards by the tapered outer surface of the needle hub thereby
generating the resultant force.

12. A safety needle pack as claimed in claim 8, wherein the slidable
sleeve has at least one cantilever arm which engages a helical track in
the outer surface of the needle hub such that, in use, as the needle is
inserted into a patient, the at least one cantilever arm is displaced
radially by the helical track in the outer surface of the needle hub
thereby generating the resultant force.

13. A safety needle pack as claimed in claim 8, wherein the safety needle
has two to six cantilever arms.

14. (canceled)

15. A safety needle pack as claimed in claim 8, wherein the receiving end
of the slidable sleeve has elastic properties and, in use, as the needle
is inserted into a patient, the resultant force is generated within the
slidable sleeve.

16. A safety needle pack as claimed in claim 8, wherein the receiving end
of the slidable sleeve is concertinaed.

17. A safety needle pack as claimed in claim 1, wherein the locking
mechanism provides substantially no resistance against the resultant
force as the slidable sleeve moves from the retracted position to the
extended position.

18. A safety needle pack as claimed in claim 1, wherein the slidable
sleeve has a first extended position where the slidable sleeve is able to
be moved towards the receiving end of the needle hub and a second
extended position where the slidable sleeve is in a locked position.

19. A safety needle pack as claimed in claim 18, wherein the locking
mechanism comprises a latching pawl on the inside surface of the slidable
sleeve capable of latching to a shoulder on the outside surface of the
needle hub when the slidable sleeve is in the second extended position.

20. A safety needle pack as claimed in claim 18, wherein an inside surface
of the slidable sleeve has a pin which engages a sprag and a resilient
pawl attached to the needle hub thereby holding the slidable sleeve in
the first extended position and, in use, allowing the slidable sleeve to
move into the second extended position.

21. A safety needle accessory as claimed in claim 1, wherein the locking
mechanism comprises one or more projections on the slidable sleeve and a
corresponding one or more holes on the needle hub such that in the
extended position after removal from the patient the one or more
projections lockably engage the corresponding one or more holes.

22. A safety needle accessory as claimed in claim 21, wherein one or more
holes on the needle hub is a circumferentially continuous hole.

23. A safety needle pack as claimed in claim 1, wherein the safety needle
pack is constructed from materials capable of being sterilized with gamma
irradiation and/or ethylene oxide.

24. A safety needle pack as claimed in claim 1, further comprising a
helical spring which, in use, generates the resultant force as the
slidable sleeve is caused to move towards the receiving end of the needle
hub and into the retracted position.

25. A safety needle pack as claimed in claim 1, wherein, the slidable
sleeve, prior to use, is not under any substantial load.

26. (canceled)

27. A safety needle pack comprising:a hollow needle having a tip for
inserting into a patient, a needle hub surrounding the hollow needle, a
slidable sleeve slidably mounted on the needle hub and a pack surrounding
the hollow needle, needle hub and slidable sleeve,the needle hub, the
slidable sleeve and the pack having a receiving end which is distal to
the tip of the needle and an injection end which is proximal to the tip
of the needle,wherein the receiving end of the needle hub is suitable for
connection to an injection device and the slidable sleeve is adapted to
slide in the direction of the length of the needle between an extended
position in which the needle tip is located inside the slidable sleeve
and a retracted position in which the needle tip projects from the
slidable sleeve, via an intermediate position between the extended
position and the retracted position, such that, in use, the slidable
sleeve is moved into the intermediate position while preparing for
injecting the needle into the patient and then as the needle is inserted
into the patient, the slidable sleeve is caused to move into the
retracted position, and in moving in to the retracted position a
resultant force is generated such that on removal of the needle from the
patient the resultant force causes the slidable sleeve to move towards
the injection end of the needle hub and into the extended position, the
safety needle further comprising a locking mechanism capable of retaining
the slidable sleeve in the extended position after removal of the needle
from the patient, andwherein the pack is releasably mounted on the needle
hub and slidable sleeve such that the injection end of the pack covers at
least the needle tip and the receiving end of the pack has an open
portion to expose the receiving end of the needle hub, and by causing the
pack to be moved in a direction towards the receiving end of the needle
hub, the pack engages with the slidable sleeve which is retracted from
the extended position to the intermediate position.

28. A safety needle pack as claimed in claim 27, wherein the needle tip is
at least partially shrouded in the intermediate position.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application is a Section 371 of International Application No.
PCT/GB2005/000357, filed Feb. 3, 2005, which was published in the English
language on Aug. 10, 2006, under International Publication No. WO
2006/082350 A1 and the disclosure of which is incorporated herein by
reference.

BACKGROUND OF THE INVENTION

[0002]This invention relates to a safety needle and in particular to
safety needle pack.

[0003]Needle stick injuries carry a significant risk of spreading
infection, such as HIV and hepatitis, and are commonplace among
healthcare workers. The USA has led the way in introducing legislation
that obliges healthcare providers to use the safest devices when giving
injections, intravenous drug administration and similar invasive
procedures. Other countries are following and, even without legislation,
the ever-present risk of litigation has alerted pharmaceutical companies
and health authorities to seek suitable safe devices.

[0004]As a result of the heightened awareness of needle stick injuries,
there have been a large number of inventions addressing this issue, some
more successful than others. Most take the form of a protective sleeve
which covers the needle tip after the injection has been given, or means
for retracting the needle rapidly into the syringe barrel. Such a safety
needles are exemplified by U.S. Pat. No. 4,911,693, U.S. Pat. No.
4,813,940 and U.S. Pat. No. 5,104,384.

[0005]A common requirement for drug administration is to draw the drug
from a vial or bulk container, or first reconstitute a lyophilised drug,
and then draw up the required volume of drug from the reconstitution
vessel. Good practice demands that separate needles are used for such
procedures, to avoid contamination and "coring" of the rubber vial
closure, and from a practical viewpoint, the needle used to draw up the
drug usually will be larger than the delivery needle.

[0006]Often it is required for the needle tip to be visible prior to
giving the injection because frequently a small amount of drug must be
aspirated to clear out trapped air, and to correct the volume after
drawing up the drug from a bulk container. Also, two of the most common
types of injection given are intradermal and intravenous, and both
require that the needle tip be visible to ensure that the tip is inserted
into the tissues or vein bevel-side up.

[0007]It is particularly problematic to provide a low-cost needle which is
able to prevent needle stick injuries, whilst allowing the tip of the
needle to be visible during injection. At present there are no such
devices on the market. There is therefore a need for a low cost safety
needle which prevents needle stick injuries in healthcare workers but
allows the tip of the needle to be exposed.

BRIEF SUMMARY OF THE INVENTION

[0008]Accordingly, the present invention provides a safety needle
comprising a hollow needle, a needle hub surrounding the hollow needle, a
slidable sleeve slidably mounted on the needle hub and a pack surrounding
the hollow needle, needle hub and slidable sleeve, the needle hub, the
slidable sleeve and the pack having a first (receiving) end which is
distal to (i.e. furthest from) the tip of the needle and a second
(injection) end which is proximal to (i.e. nearest to) the tip of the
needle, wherein the receiving end of the needle hub is suitable for
connection to an injection device and the slidable sleeve is adapted to
slide in the direction of the length of the needle between an extended
position in which the injection end of the needle is located inside the
slidable sleeve and a retracted position in which the injection end of
the needle projects from the slidable sleeve, via an intermediate
position between the extended position and the retracted position in
which the injection end of the needle projects partially from the
slidable sleeve, such that, in use, the slidable sleeve is moved in to
the intermediate position for injection in to a patient and then as the
needle is inserted into a patient, the slidable sleeve is caused to move
into the retracted position, and in moving in to the retracted position a
resultant (or restoring) force is generated such that on removal of the
needle from the patient the resultant force causes the slidable sleeve to
move towards the injection end of the needle hub and into the extended
position, the safety needle further comprising a locking mechanism
capable of retaining the slidable sleeve in an extended position after
removal of the needle from the patient, and wherein the pack is
releasably mounted on the needle hub and slidable sleeve such that the
injection end of the pack covers at least the injection end of needle and
the receiving end of the pack has an open portion to expose the receiving
end of the needle hub, and by causing the pack to be moved in a direction
towards the receiving end of the needle hub, the pack engages with the
slidable sleeve which is retracted from the extended position to the
intermediate position.

[0009]This safety needle pack protects the user from needle stick injuries
while the safety accessory, namely the needle hub and the slidable
sleeve, are primed for use. By priming the safety accessory for use, the
slidable sleeve is caused to move in to an intermediate position between
the extended and retracted positions such that the needle bevel is
exposed.

[0010]The present invention also provides a method for priming an
injection device comprising the steps of inserting an injection device in
to the receiving end of the needle hub of the safety needle pack as
claimed in any preceding claim, moving the pack towards the injection
device such that the slidable sleeve moves in to the intermediate
position, and removing the pack.

[0011]The present invention further provides a method for injecting a
patient using the safety needle pack as defined above.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0012]The foregoing summary, as well as the following detailed description
of the invention, will be better understood when read in conjunction with
the appended drawings. For the purpose of illustrating the invention,
there are shown in the drawings embodiments which are presently
preferred. It should be understood, however, that the invention is not
limited to the precise arrangements and instrumentalities shown.

[0013]In the drawings:

[0014]FIG. 1 shows a safety needle attached to a syringe without the pack;

[0015]FIG. 2 shows a centre line cross-section through the safety needle
attached to a syringe;

[0017]FIG. 4 shows a safety needle with the slidable sleeve in an extended
and locked position;

[0018]FIG. 5 shows the detent mechanism;

[0019]FIG. 6 shows the receiving end of the slidable sleeve showing the
cantilever arms;

[0020]FIG. 7 shows the barrel of a typical glass syringe used commonly for
pre-filling with a drug, assembled with a safety needle;

[0021]FIG. 8 shows an integral syringe barrel and needle hub;

[0022]FIG. 9 shows a safety needle as assembled by the manufacturer, prior
to inserting it into its pack;

[0023]FIG. 10 is a centre-line section of the safety needle in its pack;

[0024]FIG. 11 shows how the pack is used to hold the safety needle when
connecting it to a syringe;

[0025]FIG. 12 shows the safety needle after removing the pack, and ready
to use;

[0026]FIG. 12a shows an alternative shroud to increase the protection
against needle stick injuries, whilst allowing the needle bevel to be
seen immediately prior to giving the injection.

[0027]FIG. 13 shows the safety needle being used to inject medicament;

[0028]FIG. 14 shows the safety needle after the injection with the
protective slidable sleeve locked in a forward position to cover the
needle tip;

[0029]FIG. 14a shows a centre-line section through the safety needle,
rotated to show the part of the locking mechanism;

[0030]FIG. 15 shows a centre-line section of a further embodiment of the
safety needle in its pack; and

[0031]FIG. 16 shows a three-dimensional representation of the hub of the
embodiment of FIG. 15.

DETAILED DESCRIPTION OF THE INVENTION

[0032]In the drawings, like parts are given the same reference numerals.

[0033]The applicants have found that the process of exposing the tip of
the needle can, in itself lead to needle stick injuries. This is
particularly undesirable where the user is injecting cytotoxic agents,
for example during cancer chemotherapy. The safety needle pack of the
present invention avoids such injuries by providing a pack which shields
the user from the needle tip whilst the tip of the needle is being
exposed, at least partially. By at least partially, means that the tip of
the needle is not exposed to the extent that it is exposed when the user
injects the needle through the skin of the patient but is exposed
sufficiently for the user to see the bevel of the needle, in order to
guide the tip in to a specific part of the patient or to aspirate air or
expel any excess drug. When the needle tip is at least partially exposed
the arrangement of the slidable sleeve and the needle hub hold the
slidable sleeve in this intermediate position.

[0034]FIGS. 1-8 exemplify a safety needle for preventing needle stick
injuries which is suitable for use with the pack of the present
invention. FIG. 1 shows the general arrangement of a safety needle 1
(i.e. the safety needle accessory and the needle 3) of the type which may
be used with the present invention as fitted to a male Luer taper
connector 4 of syringe 2, with the end of the hollow (e.g. hypodermic)
needle 3 enclosed by the slidable sleeve 5. The slidable sleeve 5 is
prevented from longitudinal movement on the needle hub 7 by a locking
ring 13, which may be removed by pulling on the tab 14. The removable
locking ring may be connected to the needle hub and/or the slidable
sleeve. Although embodied in the Figures as cylindrical, the cylindrical
shape of the needle hub and slidable sleeve may be replaced by
triangular, rectangular or other shapes to suit the application.

[0035]FIG. 2 is a cross-section through the axis of the safety needle 1.
The needle hub 7 is cylindrical and terminates at the end which receives
the syringe with a conical section 8, and is moulded onto the needle 3.
The conical section 8 has an inner female Luer cone 24 which is shown
frictionally attached to the male Luer cone 4 of syringe 2 (the Luer
system for attaching the needle to the syringe has two main forms, that
is a taper friction fit and a screw thread and both are included in the
present invention). The cylindrical slidable sleeve 5 shrouds the needle
3 and the needle hub 7, and is freely sliding on and guided by the needle
hub 7. At the receiving end (i.e. the end which receives the syringe) of
slidable sleeve 5, there are four cantilever arms 9 which bear
resiliently upon the surface 18 of the conical section 8. The slidable
sleeve 5 is free to slide on the needle hub 7, but is temporarily
prevented from doing so by the locking ring 13. Locking ring 13 is
moulded integrally with the slidable sleeve 5 by a frangible joint 15,
and may be partially or wholly detached by pulling on the tab 14 to break
the frangible joint 15. It is preferred that the ring 13 remains attached
to the slidable sleeve 5 to reduce the number of discarded parts. In
addition, the frangible joint provides a tamper-evident lock.
Alternatively, the locking ring 13 may be moulded to the needle hub 7 via
a suitable frangible connection. When the locking ring 15 is removed, as
shown in FIG. 3 the slidable sleeve 5 may be pushed in the direction of
arrow X by acting on the face 6, when it will move relative to the needle
hub 7 to expose the needle 3. As the slidable sleeve 5 moves, the
cantilever arms 9 are forced outwards by the surface 18 of the conical
section 8. The cantilever arms 9 are resilient and the reaction force
against the surface 18 produce a resultant force Y acting against arrow
X, so that when the original force is removed, the slidable sleeve 5
returns to cover the tip of needle 3.

[0036]Since the resultant force is provided by the slidable sleeve 5
itself, no separate spring, e.g. a helical spring, is required in this
embodiment although a separate spring could be used if desired. Thus, the
resultant force may be generated within the slidable sleeve, for example
by the sleeve having an elastically deformable portion, and/or by the
accessory further comprising an elastically deformable member, such as a
spring.

[0037]As shown in FIG. 6, the cantilever arms 9 may have pads 17 which
bear onto the surface 18 and, by suitably designing the bearing surfaces
of the pads 17, various spring characteristics may be obtained. Although
four cantilever arms 9 are shown, any number could be employed. At least
one cantilever arm 9 is required for this embodiment although 2 to 6 are
preferred and particularly preferably four.

[0038]Although the surface 18 is exemplified by a conical surface, other
embodiments may be used within the scope of the present invention. In the
Figures, the surface is straight, i.e. substantially conical by which the
applicant means sufficiently conical to generate a resultant force,
however, the surface need not be straight as shown, but may be curved to
give a more linear return rate. Thus the force Y could be substantially
constant over a reasonable working stroke of the slidable sleeve 5. In
addition, the whole surface 18 of the receiving end of the needle hub 17
need not be conical. In fact just one tapered section, e.g. a tapered
ridge, would be sufficient. The tapered section does not have to project
from the surface of the needle hub 7. The tapered section could also
descend into the wall of the needle hub, i.e. a tapered detent rather
than a tapered ridge. Also, as described below with reference to FIG. 8,
provided the slidable sleeve 5 is suitably configured, a projection in
the surface 18 of the needle hub 7 will suffice.

[0039]These different arrangements provide a great deal of design
flexibility in the safety needle accessory of the present invention. For
example, the linearity of the return rate may be varied depending on the
particular requirements for a particular application.

[0040]Referring to FIG. 4, when the slidable sleeve 5 returns in direction
Y, it travels slightly past its original staring position, so that the
resilient pawl 20 which was depressed by the surface 25 of hub 7, snaps
out to act against face 16 of hub 7. This ensures that the slidable
sleeve 5 cannot be pushed back towards the syringe 2, and therefore the
needle 3 is safely covered. It is preferred that there is a pre-load
between the cantilever arms 9 and hub 7 to ensure that the slidable
sleeve 5 is sufficiently biased in the direction of arrow Y to complete
its full displacement potential.

[0041]The slidable sleeve preferably has a first extended position where
the slidable sleeve is able to be moved towards the receiving end of the
needle hub and a second extended position where the slidable sleeve is in
a locked position. The different start and finish positions of the
slidable sleeve 5 is achieved by a detent mechanism shown in FIG. 5,
which is to be read in conjunction with FIGS. 2, 3 and 4. After the first
two or three millimetres of movement, a detent integral with the slidable
sleeve "switches" so that the return of the slidable sleeve trips a
latching pawl, so that the slidable sleeve returns only to the "safe"
position; that is the pawl prevents the slidable sleeve from being moved
towards the syringe a second time, and thus protects the tip of the
needle. As part of the detent mechanism, an inside surface of the
slidable sleeve has a pin 10 which engages a sprag 26 and a resilient
pawl 19 attached to the needle hub 7 thereby holding the slidable sleeve
in the first extended position and, in use, allowing the slidable sleeve
to move into the second extended position. Pin 10 is integral or attached
to the slidable sleeve 5. Sprag 26, resilient pawl 19, and recess 27 are
moulded integrally with the needle hubs 7, 8, and the pin 10 extends into
the recess, and allowed to move freely except where controlled by the
detent and the boundaries of the recess. In the initial assembly of the
safety needle, the slidable sleeve 5 is placed over the needle 3 with pin
10 proximate to the sprag 26 (formed as part of the needle hub 7) at
position a (FIG. 5). As the slidable sleeve 5 is moved further, the pin 5
deflects the resilient pawl 19, until the pin 10 is trapped behind sprag
26 at position b. In this position the slidable sleeve 5 is trapped on
the needle hubs 7, 8 and cannot be removed without applying considerable
force. This is the position of the components as supplied to the end
user, and the location of the locking ring 13 takes account of this. With
the locking ring 13 removed, the slidable sleeve 5 is pushed further
towards the syringe 2, and pin 10 again deflects the resilient pawl 19
until the pin 10 reaches position c. This distance j defines the initial
displacement of the slidable sleeve 5, when starting the injection, and
the tip of needle 3 may be level with the face 6 of slidable sleeve 5.
The slidable sleeve 5 may now be moved towards the syringe until the pin
10 reaches the end wall 28 of the recess 27 at position d. This position
defines the maximum displacement of slidable sleeve 5, and thus the
maximum exposure of the needle 3. At any time the force acting on
slidable sleeve 5 is removed, the slidable sleeve 5 will return in the
direction of arrow Y until pin 10 reaches the position e. Pin 10 would
also help prevent the removal of slidable sleeve 5, but additionally the
tooth 21 is now proximate to face 22 on a cantilever arm 9, which
prevents the removal of the slidable sleeve 5. In this final position,
pawl 20 engages with face 16 of hub 7 and prevents the slidable sleeve 5
from being moved. It should be noted that with the present diagrammatic
presentation of the safety needle, a small amount of rotational movement
is necessary between the slidable sleeve 5 and hub 7 to permit the pin 10
to move from position c to position e, but the rotation is preferably
negligible.

[0042]The detent mechanism is interchangeable between the slidable sleeve
5 and needle hub 7 if required. Also, the detent mechanism described
hereinabove is but one of a number of such mechanisms, the main
requirement being to permit the following sequence of operation: permit
the slidable sleeve to be moved sufficiently so that the opening in the
slidable sleeve is level with or just in front of the needle tip, at
which position the detent must be activated so that if the displacing
force on the slidable sleeve is removed, the slidable sleeve slides
forward and locks, thus protecting the user from contact with the needle
tip. Typically, the tip of the needle would be about 3 mm back from the
face of the opening in the slidable sleeve at the start, and 1 mm back
from the face when the detent is activated.

[0043]FIG. 7 shows the device 1 as previously described, except that in
this embodiment the needle 3 is bonded into the outlet end of the syringe
barrel 29. The needle is free to pass through the needle hub 7, and the
cone 9 is adapted at 31 to snap-fit over the projection 30. The form of
projection 30 is produced as a result of rolling the glass onto a
mandrel, whereby the excess glass is forced in to the shape as shown.
Alternatively, a more defined snap-fitting termination may be formed, the
object being to make the device 1 difficult to remove after assembling it
to the syringe barrel.

[0044]FIG. 8 shows a safety needle 1 in which the needle hub 7 is integral
with the barrel of the syringe 2. The slidable sleeve 5 is then attached
to the needle hub 7 in the manner as described hereinbelow. The material
of the needle hub 7, which also constitutes the barrel of the syringe,
would, of course, have to be made from a drug-compatible material.

[0045]As mentioned hereinabove, FIG. 8 also shows the separate feature of
the projection 32 on the surface 18 of the needle hub 7 which may be used
to deflect the slidable sleeve 5 thereby generating the resultant force.
This embodiment, i.e. incorporating the projection 32, provides a highly
non-linear return rate since the length of the slidable sleeve 5 is
effectively reduced as the slidable sleeve 5 and the needle hub 7 are
slid together, thereby increasing the stiffness of the slidable sleeve 5.

[0046]As an alternative to the tapered outer surface of the needle hub 7,
the slidable sleeve has at least one cantilever arm which engages a
helical track in the outer surface of the needle hub such that, in use,
as the needle is inserted into a patient, the at least one cantilever arm
is displaced radially by the helical track in the outer surface of the
needle hub thereby generating the resultant force. Thus, as the slidable
sleeve 5 is caused to move towards the receiving end of the needle hub 7,
one or more cantilever arms 9 are forced to follow the direction of the
helical tracks. Since the cantilever arms 9 are resilient, a resultant
force will be generated.

[0047]As an alternative to cantilever arms, the receiving end of the
slidable sleeve itself may have elastic properties such that, in use, as
the needle is inserted into a patient, the resultant force is generated
within the slidable sleeve. By elastic properties the applicant means
that the resultant force is generated within a radially continuous
slidable sleeve, i.e. a sleeve without cantilever arms. The elastic
properties may be achieved by using an elastic material, such as an
elastomeric polymer. Alternatively, the receiving end of the slidable
sleeve may be concertinaed, with the ridges, of course, running parallel
to the hollow needle. The elastic properties could also be generated
using a circumambient spring attached to the slidable sleeve.

[0048]As a further alternative, instead of the resultant force being
generated in the slidable sleeve 5 itself, the safety needle may
incorporate an alternative, or additional, resultant mechanism, such as a
helical spring. Such safety needles are exemplified in U.S. Pat. No.
4,911,693, U.S. Pat. No. 4,813,940 and U.S. Pat. No. 5,104,384.

[0049]FIGS. 9-14a show an embodiment of the present invention in which the
needle hub and the slidable sleeve are adapted to allow the slidable
sleeve to be retracted into and held at an intermediate position between
the extended position and the retracted position such that, in use, the
tip of the needle 2 projects partially from the slidable sleeve, that is
the needle bevel is exposed. In this intermediate position the locking
mechanism is not engaged and hence the slidable sleeve may be retracted
further into the (fully) retracted position as it is inserted into the
patient. The advantages of this arrangement are that exposing the tip of
the needle partially allows the user to position the needle more
precisely on, for example, the patient's skin, and also facilitates the
aspiration of trapped air and excess drug. The use of the pack prevents
needle stick injuries when the safety needle is in the intermediate
position.

[0050]FIG. 9 shows the device as assembled by the manufacturer, and
comprises a needle hub 7, being of conical or other tapering form.
Slidable sleeve 5 has cantilever arms 9 attached or integral, the arms
terminating with a projection 33, which engages with undercut 34 of the
needle hub 7, shown in greater detail in FIG. 9a. In the position shown,
there is little load on the spring cantilever arms 9, but sufficient to
hold the components together. Referring to FIG. 10, this is a centre-line
cross-section through the safety needle assembled into its pack 35. Pack
35 is releasably mounted on the needle hub and slidable sleeve, that is
the accessory is held within the pack 35, for example by friction, but
may be removed by the user. To facilitate the releasable mounting the
pack and accessory have engageable portions which may simply be the
surfaces of the pack and accessory. These surfaces may be textured or
have projections. The pack 35 preferably tubular and also preferably made
from a deep-drawn vacuum formed plastics material. The pack 35 is shown
with a flange 36 and open at the receiving end of the needle hub 7, and
closed at the injection end by the extension 37. The inner face of
shoulder 38 rests on the end face of the slidable sleeve 5. The needle
hub 7 has one or more projections 39, which provide a light frictional
retaining force on the inside of the pack 35 to prevent the safety needle
from falling out. The safety needle may be further retained inside the
pack 35 by a releasable (peel-off) membrane 40, which is preferably gas
permeable. The membrane 40 is bonded to flange 36, and may be made from a
porous material such as Tyvek® which is spun-bonded high-density
polyethylene available from DuPont and which is used extensively in
pharmaceutical packaging to permit a sterilizing gas, such as ethylene
oxide, to penetrate the pack whilst preventing ingress of bacteria during
storage. Other peelable materials may be used according to the
sterilization process used. The membrane 40 may have a tag 41 to assist
removal. The needle hub 7 has a syringe adaptor 24 which may be
configured to suit the common Luer taper or threaded Luer lock syringe
nozzles.

[0051]Referring to FIG. 11, to assemble the safety needle to a pre-filled
syringe 42, the user removes the peelable membrane 40 by pulling on tag
41. Holding the pack 35, the user pushes the adaptor 24 of the needle hub
7 in the direction of the arrow X onto the syringe connector 43. This
causes the inner face of the shoulders 38 to press against face of
slidable sleeve 5 which moves towards the syringe. The injection end of
the pack 35 has an extended portion which is capable of housing the tip
of the needle 3 in the intermediate position and the shoulders 38 of the
extended portion abut against the injection end of the slidable sleeve
thereby causing the slidable sleeve 5 to move in to the intermediate
position when the pack 35 is caused to move towards the receiving end of
the needle hub 7. At the same time, the cantilever arms 9 are forced
outwards as they travel up the surface of the needle hub 7, until the
small shoulder 44 on the slidable sleeve 5 reaches the projection 45 on
the needle hub 7, thus preventing further movement. At or about this
point, at least one of the projections 33 snaps over a catch 46 on the
needle hub 7. The cantilever arms 9 are now loaded radially, and exerting
a resultant force urging the slidable sleeve 5 off the needle hub 7. The
pack 35 may now be removed, and catch 46 prevents the slidable sleeve 5
from coming off the needle hub 7 through the resultant force of the
cantilever arms 9. With pack 35 removed, the safety needle will appear as
shown in FIG. 12, and is ready for use. The tip needle 3 is thus
partially exposed, i.e. the bevel of the needle may be seen by the user
projecting from the slidable sleeve 5, and the user may aspirate trapped
air and excess drug. FIG. 12a shows the safety needle ready for use, as
in FIG. 12, but with an extension 47 on face of slidable sleeve 5
extended to shroud partly the tip of the needle 3, which will afford more
protection, but make aspiration of air and excess drug slightly more
difficult.

[0052]Referring to FIG. 13, the user pushes the needle 3 in the direction
of arrow A through the patient's epidermis 48 and into the subcutaneous
tissue 49, which brings the face of the slidable sleeve 5 into contact
with the stratum corneum of the patient's epidermis 48. Further movement
in the direction of arrow A pushes the slidable sleeve 5 towards the
syringe 42, and thus the cantilever arms 9 are forced further outwards by
the conical surface of the needle hub 7. At the same time, the end of at
least one cantilever arm 9 is forced against a cam 50 which causes the
slidable sleeve 5 and cantilever arms 9 to rotate in the direction of
arrow B, until the end of cantilever arm 9 drops into the groove 51.
Groove 51 has a slope towards the needle, which maintains the resultant
force of the cantilever arm 9. At this point, (which represents only a
millimetre or two of movement of the slidable sleeve 5), if the safety
needle is withdrawn from the patient, the resultant force of the
cantilever arms 9 urges the slidable sleeve 5 towards the tip of the
needle 3 until the tip of the needle 3 is shielded by the slidable sleeve
5. At the end of travel of the projection 33 and the cantilever arm 9,
the projection 33 on cantilever arm 9, which is still sliding in the
groove 51, drops into the hole 52. This locks the slidable sleeve 5 in
position and prevents the slidable sleeve 5 being pushed back towards the
syringe 42, or being pulled off the needle hub 7. This position is shown
in FIGS. 14 and 14a, the latter being a section through the centre-line,
and the safety needle rotated to show the grooves 51 and holes 52, with
the projections 33 on cantilever arms 9 located within the holes 52.
Although the lockably engaging projection 33 and hole 52 are shown with
reference to cantilever arms 9, any slidable sleeve 5 may be locked into
position using one or more projections 33 and corresponding one or more
holes 52. Such an arrangement results in a less complex, and hence less
costly, safety needle accessory and avoids introducing opposing
frictional and/or detent forces which result from an integral but
independent locking mechanism. An advantage of the projection 33/hole 52
mechanism is that the locking mechanism provides substantially no
resistance against the resultant force as the slidable sleeve 5 moves
from the retracted position to the extended position. When the slidable
sleeve 5 reaches the extended position the locking mechanism engages
which then resists the resultant force.

[0053]The protective pack 35 confers safe storage and handling advantages,
allows the safety needle to be assembled to a syringe without risking
premature operation of the safety mechanism, and does not add to the
overall cost of the device, since it is similar to the vacuum-formed
packs already in use for needles and syringes. For the user, the
operation of the safety needle is practically identical to the use of a
standard needle.

[0054]It is preferable that the coefficient of friction between the
slidable sleeve 5 and the needle hub 7 is low, so that the resultant
biasing force to return the slidable sleeve is not compromised by
"stiction", or so high that the force required on the patient's skin to
deflect the slidable sleeve 5 is excessive. This may be achieved by
careful selection of materials. Such materials are known in the art, for
example, the needle hub could be made from a high-density polyethylene or
similar drug-compatible plastics material, and the slidable sleeve from
an inexpensive plastics material such as polycarbonate, polystyrene,
polyester or PVC. A more expensive, highly creep-resistant plastics
material, for example polyphenylene sulfone, could also be used. As an
alternative, the slidable sleeve, or just the at least one cantilever
arm, may be made from metal, preferably stainless steel. The metal would
be fabricated sufficiently thinly to provide the required elastic
properties. If necessary, a lubricant may be used, or a lubricant may be
incorporated with the polymers. Generally the materials should be
suitable for sterilization by gamma radiation, but it is possible to
select materials compatible with sterilization by steam or other gas such
as ethylene oxide.

[0055]In a preferred embodiment, the slidable sleeve, prior to use, is not
under any substantial load. Any substantial load indicates a load which
is sufficient to cause the material of the slidable sleeve to undergo
creepage during storage at ambient temperature.

[0056]FIGS. 15 and 16 show a further embodiment of the present invention
in which the needle hub and the slidable sleeve are adapted to allow the
slidable sleeve to be retracted into and held at an intermediate position
while the needle is still contained within the pack. This embodiment
further allows the accessory to be stored without any substantial load on
the slidable sleeve 5 thereby preventing creepage during storage.

[0057]FIG. 15 shows a centre-line cross-section through the safety needle
1 assembled into its pack 35 and FIG. 16 shows a three-dimensional
representation of the needle hub 7. Pack 35 is releasably mounted on the
needle hub 7 and slidable sleeve 5. The pack 35 preferably tubular and
also preferably made from a deep-drawn vacuum formed plastics material.
The pack 35 is shown with a flange 36 and open at the receiving end of
the needle hub 7, and closed at the injection end by the extension 37
defined by a plurality, e.g. six, ribs 53. The ribs 53 rest on the end
face of the slidable sleeve 5. The needle hub 7 has one or more
projections 39, which provide a light frictional retaining force on the
inside of the pack 35 to prevent the safety needle from falling out. The
pack 35 may also have a partially textured internal surface 54 which
engages the projections 39 in order to prevent rotation of the accessory
1 within the pack. The safety needle may be further retained inside the
pack 35 by a releasable (peel-off) membrane 40 as described hereinabove.
The needle hub 7 has a syringe adaptor 24 which may be configured to suit
the common Luer taper or threaded Luer lock syringe nozzles.

[0058]In the position shown in FIG. 15, the device is as assembled by the
manufacturer. Slidable sleeve 5 has cantilever arms 9 attached or
integral, the arms terminating with a projection 33, which engages with
indent 55 of the needle hub 7. The indent 55 is of sufficient depth that
the cantilever arms 9 are under substantially no load, i.e. the sleeve 5
is not radially expanded. In this position, the sleeve 5 is prevented
from sliding off the needle hub 7 by the pack 35 and the engagement
between the projection 33 on the cantilever arms 9 and the indent 55 on
the hub 7.

[0059]To assemble the safety needle to a pre-filled syringe 42, the user
removes the peelable membrane 40 by pulling on tag 41. Holding the pack
35, the user pushes the adaptor 24 of the needle hub 7 onto the syringe
connector 43. This causes the inner face of the ribs 53 to press against
face of slidable sleeve 5 which moves towards the syringe. The injection
end of the pack 35 is capable of housing the tip of the needle 3 in the
intermediate position. The ribs 53 of the pack 35 abut against the
injection end of the slidable sleeve thereby causing the slidable sleeve
5 to move in to the intermediate position when the pack 35 is caused to
move towards the receiving end of the needle hub 7. The indent 55 has a
tapering interior surface which causes the sleeve to expand radially as
the sleeve 5 is caused to move up the surface of the needle hub 7. The
sleeve 5 is caused to move until the sleeve 5 is in the intermediate
position wherein the needle tip is partially exposed. At or about this
point, at least one of the projections 33 snaps over a catch 56 on the
needle hub 7. The cantilever arms 9 are now loaded radially, and exerting
a resultant force urging the slidable sleeve 5 off the needle hub 7. This
resultant force is countered by the catch 56 on the hub 7. The pack 35
may now be removed, and catch 56 prevents the slidable sleeve 5 from
coming off the needle hub 7 through the resultant force in the cantilever
arms 9. With pack 35 removed, the safety needle is ready for use. The tip
needle 3 is thus partially exposed, i.e. the bevel of the needle may be
seen by the user projecting from the slidable sleeve 5, and the user may
aspirate trapped air and excess drug.

[0060]The user pushes the needle 3 through the patient's epidermis and
into the subcutaneous tissue, which brings the face of the slidable
sleeve 5 into contact with the stratum corneum of the patient's
epidermis. Further movement of the needle into the patient's skin pushes
the slidable sleeve 5 towards the syringe 42, and thus the cantilever
arms 9 are forced further outwards by the conical surface of the needle
hub 7. At the same time, the end of at least one cantilever arm 9 is
forced against a cam 57 which causes the slidable sleeve 5 and cantilever
arms 9 to rotate (in an analogous manner to FIG. 14), until the end of
cantilever arm 9 is directed along the guide 58. As shown in FIG. 16, the
catch 56 and the cam 57 are preferably formed into a single structure.
The projection 33 follows guide 58 as the sleeve is caused to retract. As
the sleeve 5 retracts, the sleeve 5 is deflected radially by the sloping
of the hub 7 towards the needle.

[0061]At this point, (which represents only a millimetre or two of
movement of the slidable sleeve 5), if the safety needle is withdrawn
from the patient, the resultant force of the cantilever arms 9 urges the
slidable sleeve 5 towards the tip of the needle 3 until the tip of the
needle 3 is shielded by the slidable sleeve 5. At the end of travel of
the projection 33 and the cantilever arm 9, the projection 33 on
cantilever arm 9, which is still following the guide 57, drops into the
hole 59. This locks the slidable sleeve 5 in position and prevents the
slidable sleeve 5 being pushed back towards the syringe 42, or being
pulled off the needle hub 7.

[0062]The hole 59 is shown further towards the injection end of the hub 7
than the indent 55. This allows the hole 59 to be a radially continuous
hole which permits free rotation of the sleeve 5 around the hub in the
locked position. This free rotation provides a more secure locked
position. In a simple hole/projection arrangement, accidental rotation of
the sleeve 5 might distort the sleeve sufficiently to disengage the hole
and projection. Allowing free rotation means that the rotation is not
resisted preserving the integrity of the locking mechanism.

[0063]As previously mentioned hereinabove, the syringe may be supplied
empty or pre-filled. When a pre-filled syringe is used, the syringe is
preferably sealed using a sealing cap or plug to prevent evaporation or
loss of the drug, excipient, carrier and/or diluent by, for example,
thermal expansion.

[0064]As well as application to a syringe, the same safety needle
accessory described herein could form the basis of a intravenous giving
set, so that the insertion of the needle into the patient's vein is
simple and safe. Indeed, the safety needle accessory of the present
invention may be used with any suitable injection device.

[0065]It will be appreciated by those skilled in the art that changes
could be made to the embodiments described above without departing from
the broad inventive concept thereof. It is understood, therefore, that
this invention is not limited to the particular embodiments disclosed,
but it is intended to cover modifications within the spirit and scope of
the present invention as defined by the appended claims.